1. Field of the Invention
The invention pertains to a filling valve for a gas bag installed in a space bounded by a rigid wall and acted on by forces of a liquid flowing into and out of the space under pressure. The gas bag serves as a compensation space and is filled with gas through an access channel aligned with an opening in the rigid wall.
2. Description of the Related Art
U.S. Pat. No. 6,116,585 discloses a gas bag made out of plastic-coated metal foil. A gas bag of this type can be used anywhere that gas-filled compensation elements can be installed in spaces bounded by rigid walls, where there is no pressure difference between any of the interior spaces of the compensation element and the exterior pressure space and thus where the wall of the compensation element must merely be flexible and is not called upon to move elastically. These conditions for compensation elements are present in hydropneumatic assemblies such as in the compensation space of a shock absorber or in the spring space of a hydropneumatic spring. Therefore, gas bags of the type disclosed in the patent can be used here. The essential point, is that during the installation and filling of this gas bag, no forces which could tear the thin wall of the gas bag may act or be exerted on the wall. In the case of shock absorbers, the gas bag is preferably filled only after the vibration-damping fluid has been introduced. For this purpose, this known design provides a filling connector, installed in the thin wall of the gas bag; during the installation, this connector is snapped into an opening in the rigid wall, i.e., in the external tube of the shock absorber. Because the gas bag is surrounded by vibration-damping fluid during operation, a lifting force acts on it, which must be at least partially absorbed by the filling connector.
The object of the present invention is to create a gas bag which, after installation in the compensation space, can be filled from the outside through a filling valve in such a way that, during filling and during operation, no forces are exerted on the gas bag wall, and the gas bag together with the filling valve can be produced, installed, and filled at low cost.
The gas bag provided with the filling valve can be easily designed in such a way that it is almost completely free of forces acting on it from the outside by locating the access channel in a connector part connected to the gas bag and by connecting this connector part to a guide part resting on the inside surface of the rigid wall, where the access channel of the filling valve is effectively connected to the opening in the rigid wall by this guide part. Thus, the lifting forces exerted on the gas bag by the vibration- damping fluid are absorbed by the guide part, and the connector part remains free of the action of any forces.
The connector part and the gas bag can be connected in an especially low- cost manner by integrating the connector part into a connecting seam located at one of the axial ends of the bag during the process of bag production. It is advantageous for this connecting seam to be made as a welded seam, although other methods of creating the connection are also conceivable. The connector part is provided with a relatively large dimension extending in the direction of the welded seam, and it is also provided with surfaces which ensure a gentle transition during the welding-in process, so that a very good, gas- tight connection is obtained. At the same time, the welded seam serves as a connection to the guide part. For this purpose, the guide part is provided with an opening which conforms exactly to the shape of the connector part and the welded seam. The connector part has a seal surrounding the access channel, this seal being pressed against the inside surface of the rigid wall.
It is advantageous for the gas bag to have attachment holes near the welded seam, which can be snapped onto corresponding retainers on the guide part. Thus the gas bag, which is produced as a flat component, assumes its approximately tubular shape as soon as it is assembled with the guide part and is held in the proper axial position by the guide part extending around the circumference, which simultaneously facilitates the installation of the gas bag in the properly oriented position in the compensation space of the shock absorber by the use of an installing device.
The gas bag can also be easily connected tightly to the guide part, at least in the axial direction, in the area of the connector part by means of a projection extending inward in the radial direction, which can be snapped into a corresponding hole in the guide part. This inward-pointing projection is advantageously provided on the connector part and can work together with a corresponding hole in the bottom sheet to ensure the exact positioning of the connector part during the production of the welded seam.
In one embodiment, the access channel in the connector part has an opening, extending radially with respect to the gas bag. This opening is located so that it can cooperate with another opening located in a cylindrical wall. A seal provided in the area of the opening is thus pressed by the guide part against the cylindrical wall, so that the opening in the cylindrical wall is connected only to the access channel during the filling process. The valve for the gas bag must prevent the gas which fills the bag from escaping through the access channel. To accomplish this, after the filling process has been completed, the guide part is pushed along the inside surface of the space until the opening present in the rigid wall is no longer in effective connection with the access channel. To ensure that the shock absorber is sealed off effectively after the guide part has been shifted, the opening should either end up between two sealing rings, which are located in grooves in the guide part, or be closed by a sealing ring.
In a highly advantageous embodiment, which makes possible a simpler overall design and also allows for trouble-free assembly, the connector part is provided with an access channel proceeding exclusively in the axial direction, this channel being located so that it can cooperate with an opening in the rigid wall proceeding in the axial direction. It is also possible without any extra effort to provide the access channel with an axially oriented connecting line, which engages in the opening or passes through the opening. A connecting line of this type can, for example, be connected to a pressure sensor and thus be used to control a device of some type as a function of the pressure. In a further simplification of the filling valve, the connector part is designed as an integral part of the guide part. A low-cost design is also obtained when the connector part is formed by the piston rod guide, in which case the piston rod guide can be preassembled with the gas bag and the filling valve to form a unit. In general, the connector part can include a valve device as an integral part. This valve device can take the form of a generally known valve, such as a mechanically opening valve or a valve consisting of elastomeric material, where the elastomer must be impermeable to the diffusion of oil and gas, and where the filling process is accomplished by means of a hollow needle, which is used to puncture the elastomer. For protection against any damage to the filling valve, the opening can be sealed by measures conventional in machine-building such as by the pressing-in of a ball.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.